The polar vortex may be on its way

The polar vortex appears to be on the move. That’s because stratospheric warming is occurring at high altitudes above the North Pole, resulting in a spike in temperatures.

That, in turn, could result in bitter cold air pushing southward into the United States within a couple of weeks, though where exactly that Arctic air will swoop down — and for how long — remains uncertain.

The polar vortex is simply a low pressure system that swirls cold air around the polar regions of the globe. But the system can sometimes move off the North Pole. In doing so, it releases cold air much farther south in regions such as North America and Europe.

The polar vortex is located in the stratosphere, about 18 miles above Earth’s surface, which is well above the jet stream, where planes fly, and where most weather occurs.

But agitations and disruptions to the flow and location of the polar vortex, like what we are seeing to the start of 2021, can influence the movement of air and weather below it. And scientists are closely watching current events for clues as to when and where the impacts will occur.

Although the term “polar vortex” has become trendy on social media in recent years, the concept is not new. It is a staple for the polar regions every year.

“Some winters, it remains fairly unperturbed. Other winters ( like this one), it can be severely disrupted/ weakened,” Jason Furtado, an assistant professor at the University of Oklahoma’s school of meteorology, said via email. “Understanding what is happening with the polar vortex is one of several features in our climate that helps meteorologists understand what to expect for winter weather over the next 2- 6 weeks.”

When the polar low pressure system is strong, it keeps the jet stream traveling around Earth in a very circular path and keeps Arctic air bundled up close to the Pole. But when that system is weakened, parts of the vortex break off and become elongated, resulting in cold air shifting southward.

When that low pressure system is weaker, the jet stream also does not have enough strength to maintain its usual path. It is that disruption in the jet stream that has a direct correlation to our weather closer to the surface.

“When the stratospheric polar vortex is strong, the jet stream tends to move further north, which keeps the cold air in the Arctic and allows relatively milder conditions across much of the United States and Eurasia,” Furtado said.

A common reason the polar vortex leaves its usual location is due to a sudden shift of hotter air, known as a sudden stratospheric warming, or SSW. This weakens the polar vortex and allows it to move.

“When the polar vortex is weak, or an SSW event occurs, then the jet stream will tend to weakened, move further south, and become ‘ wavier,’ ” Furtado said. “The effect of these changes is for warmer than normal air to move into the Arctic, colder weather to enter North America and Europe/Asia, and more extreme weather and storms overall in the middle latitudes (e.g., snowstorms).”